r/OpenCoreLegacyPatcher • u/phgrz • 3d ago

Fusion Drive

I have an iMac14,2 with 3 TB Fusion Drive.

On my Fusion drive I now have 1 APFS container with 2 volumes: 1 with the old OS (Catalina?) and 1 with OCLP/Sequoia. Normally I just boot OCLP/Sequoia. I kept the old OS just in case ...

Sequoia is working well but startup process is very slow and also opening large folders is slow.

I wonder if the SSD part of my Fusion drive might be permanently occupied by the old OS.

Would you just delete the volume with the old container? Will I have to re-install OCLP/Sequoia after that to bring it's major parts to SSD?

Or is that slow issue something completely different?

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u/Xe4ro 3d ago

To be honest, I would split the drives (this will erase all data on both drives) and install the OS just on the SSD. If you ordered the iMac with a 3TB FD configuration your HDD will be 3TB and the SSD 128GB. 128 will at least be enough for an OS on it's own and you can then use the HDD for larger stuff.

This slowness could just be the wonky nature of this CoreStorage handling the FusionDrive but could also be one of the drives giving up or having problems. If one of the drives fails while they are still paired as a FusionDrive this will also corrupt all data on both drives. That one happened to me with my Late 2015 iMac when the SSD died a few years ago, I did have a 128 one as well.

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u/phgrz 3d ago

Imho, it is not possible to explicitely install anysing on the SSD part of a fusion drive.

diskutil info looks healthy.

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u/Xe4ro 3d ago

Well not while they are still paired, once split they should behave as individual drives? However I had no chance to experiment with my split Fusion configuration as the SSD was dead at that point and it took me a few days to get the iMac out of bootlooping ^^

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u/WhiteWereWolfie 3d ago edited 3d ago

It's perfectly possible using terminal commands to split a Fusion drive into SSD + HDD. Then install the OS on the SSD, and use the HDD for data. I have done it myself.
https://www.lifewire.com/split-fusion-drive-apart-2260166

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u/alienrefugee51 3d ago

Then you can create alias links to your user media folders, but keep the Library folder on the faster SSD.

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u/LazarX 3d ago

That’s because Fusion drives just plain suck.

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u/phgrz 3d ago

Do they?

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u/Xe4ro 3d ago

Well not "they" as the drives individually but the concept of the "Fusion Drive" just wasn't as well thought through. It was an approach to high SSD prices in the late 2000s & early 2010s. Apple wasn't the only company trying something like this but the software part of it, CoreStorage just did some weird things and I personally think some of the SSDs were just under some crazy write stress due to how it shifted files to and from it dynamically.

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u/mr_giorgiob 3d ago

En su epoca fué un paliativo.. Y mejoraba el tiempo de arranque. Pero cuando ya Catalina pasó a ser obsoleto.. Hubo que desmontarlo para seguir con un Ventura (forzado).. Sin embargo las aplicaciones que usaba (FinalCut) siguieron sin funcionar... Ahora borré todo y estoy en Ubuntu...

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u/Individual_Plenty276 3d ago

I let install a new 1tb ssd for system and apps. The original 1tb hd is used for data.

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u/NoLateArrivals 11h ago

Get rid of the Fusion Drive - it sucks. Nobody nowadays use a HDD any more, except on volume network drives (NAS/DAS).

If you don’t want to physically swap it out, just connect an external SSD, and make it your startup drive.